Distance and displacement both refer to movement, but they are not the same. Distance is a scalar quantity that just tells you how much ground an object has covered, regardless of direction. On the other hand, displacement is a vector quantity that not only states the length of the path but also the direction an object has moved from its initial to final position.

Speed refers to how fast an object is moving, regardless of its direction. It is a scalar quantity, meaning it only represents magnitude and not direction.

A calculation of speed involves the division of distance covered by the time taken. It can be expressed in various units such as metres per second (m/s), kilometres per hour (km/h), or miles per hour (mph).

Velocity, like displacement, is a vector quantity. It gives both the speed of an object and its direction of movement. The formula to calculate velocity is displacement divided by time taken.

Keep in mind that constant speed means the speed is unchanging. That is different from a constant velocity, which implies that an object moves at a constant speed in a constant direction.

Acceleration comes into play when there is a change in velocity. This could be as a result of changing speed or changing direction. It's calculated by dividing the change in velocity by time taken for the change.

A positive acceleration means an increase in velocity whereas a negative acceleration (deceleration) represents a decrease in velocity.

Remember: whilst you may be moving at a high speed, if your direction is changing, your velocity is as well. For example, when you're spinning in a circle, your velocity is constantly changing, even though your speed might remain constant.

Graphical representations are useful in illustrating distance-time and velocity-time relations. A steep gradient in a distance-time graph indicates a high speed, while a horizontal line suggests no movement. On a velocity-time graph, a steep gradient represents high acceleration, while the gradient itself gives the value of acceleration. The area under the graph gives the displacement of the object.